The present invention generally relates to a photoelectric conversion semiconductor device, and in particular to a photoelectric conversion semiconductor device in which photoelectric conversion elements and a driving circuit for sequentially driving the photoelectric elements to read out data therefrom in sequence are formed on a single substrate.
Currently, various photoelectric conversion semiconductor devices have been proposed and marketed. One of the most popular examples of these is a contact-type line image sensor of a size corresponding to a size of a sheet of a paper to be optically scanned. The contact-type line image sensor is widely used as a photo sensor or an image sensor in a facsimile machine, a copying machine, an optical character reading apparatus, an electronic blackboard and the like. The contact type line image sensor has a plurality of photoelectric conversion elements formed in a line. Each of photoelectric elements includes as a photoelectric film, an amorphous film made of Cd-CdSe and Se-As-Te, for example.
Recently, a contact type line image sensor using amorphous Si has been proposed. Use of amorphous Si makes it possible to produce an image sensor of a relatively large size and a good responsibility of photoelectric conversion, compared to the image sensors using other amorphous materials. For example, there is proposed an amorphous Si: H image sensor of a sandwich type, in which an amorphous Si: H film is sandwiched between an upper transparent film and a lower transparent film.
Generally, in addition to the photoelectric elements, the image sensor is built with selection switching elements and a driving circuit. Each of the selection switching elements is coupled with the respective photoelectric elements which are aligned in a main scanning direction. The driving circuit is used to control ON/OFF states of the selection switching elements to read out data from the photoelectric elements in sequence. The driving circuit is generally constituted by a shift register. The shift register is made up of delay elements which are cascade-connected. Each of the delay elements supplies a sensor read signal to the respective selection switching elements coupled with the photoelectric elements.
Conventionally, the photoelectric elements, selection switching circuits and driving circuit are separately manufactured. They are mounted on a supporting base of the image sensor and electrically connected with each other. However, the above constitution of the image sensor has a disadvantage in that it is difficult to make image sensors of a compact size and the production process is complex. In addition, connection lines for connecting the photoelectric elements, the selection switching elements and the driving circuit together may be lengthened, which may cause noise in video signals read from the photoelectric elements.
In order to eliminate the above problems, there has also been a proposed image sensor in which the photoelectric elements, the selection switching circuits and the driving circuit are provided on a single insulating and transparent substrate. However, such a proposal does not include any detailed structure of the driving circuit nor a layout thereof on the substrate.